We are studying the submicrometer size range of inorganic aerosols formed during coal combustion and their interaction with sulfur dioxide. Pure metal oxides (Zn, Cu, V, Mn, Si) are generated in high temperature furnaces to study effects of combustion variables on size, shape, surface area, and chemical composition. Inhalation exposures are to these aerosols alone and combined with sulfur dioxide. Sulfur dioxide can be added at furnace temperatures and at room temperatures. ESCA will be used to determine the presence or absence of sulfate and/or sulfite on the aerosols. Silica particles will be coated with trace metals to simulate the surface enrichment found in coal combustion aerosols. Coals characterized as to physical factors and mineral content are burned in an experimental furnace. The effect of gas temperature, particle temperature, and oxygen partial pressure on vaporization and elemental composition of the various size fractions of the coal combustion aerosols is examined. The submicrometer fraction of these coal combustion products will be used for inhalation exposures. Data from toxicological studies are correlated to evaluate the biological response to these atmospheres. Guinea pigs and rats will be used as experimental animals. Pulmonary function studies include mechanics of respiration in unanesthetized guinea pigs during exposure and lung volumes, dynamic compliance and CO diffusing capacity in anesthetized rats following exposure. Deposition, clearance, and biological distribution of metal aerosols and coal combustion products will be studied. Methods include radiolabelled aerosols and post exposure irradiation of freeze dried lungs in the reactor. Histopathological studies following exposure include special staining, histochemistry, and uptake of tritiated thymidine.